Polycarbonates are well known thermoplastic materials which, due to their many advantageous properties, find use as thermoplastic engineering materials in many commercial and industrial applications. The polycarbonates exhibit, for example, excellent properties of toughness, flexibility, impact resistance and high heat distortion temperatures. The polycarbonates and their preparation are disclosed, for example, in U.S. Pat. Nos. 3,028,365; 3,334,154; 3,275,601 and 3,915,926.
There is, however, a need in certain applications, such as those involving a high temperature environment, for polycarbonates exhibiting even higher heat distortion temperatures than those possessed by presently available polycarbonates. It is known to increase the heat distortion temperatures of polycarbonates by adding thereto various polymer systems which exhibit high heat distortion temperatures such as polyarylates, polysulfones, and the like. These resulting blends, however, suffer from certain disadvantages such as being opaque, undergoing phase separation and delamination, and loss of certain unique properties of unblended polycarbonates such as impact strength and the like.
There thus exists a need for polycarbonates exhibiting improved heat distortion temperatures while simultaneously retaining, to a substantial degree, substantially most of the other advantageous properties of conventional polycarbonates. It is, therefore, an object of the instant invention to provide polycarbonates exhibiting improved heat distortion temperatures.